Efficient way to add a singleton dimension to a NumPy vector so that slice assignments work

Question

In NumPy, how can you efficiently make a 1-D object into a 2-D object where the singleton dimension is inferred from the current object (i.e. a list should go to either a 1x

Answer 1

What about expand_dims?

np.expand_dims(np.array([1,2,3,4]), 0)

has shape (1,4) while

np.expand_dims(np.array([1,2,3,4]), 1)

has shape (4,1).